Project Summary/Abstract In the United States, rates of new HIV infections have remained stable among men who have sex with men (MSM) in recent years despite declines among most other at-risk groups, highlighting the continued need for innovative approaches to prevention for MSM. Alcohol use is a major risk factor for HIV infection among MSM, in part due to the tendency for heavy drinking to increase the odds of engaging in sex that can transmit HIV. Our work has also shown that heavy drinkers are less likely to have tested for HIV within CDC-recommended intervals. This level of drinking is common among MSM, with up to 40% reporting heavy drinking in the past month. Home-based HIV and STI self-testing is a promising strategy for encouraging regular testing. Regular testing can help detect more new infections earlier, preventing onward infections and improving mortality. Despite self-testing?s promise, little is known about the best ways to provide support alongside HIV/STI self- testing programs. Although many current self-testing programs provide recipients with access to a 24-hour helpline they can call for counseling and referrals, few use this service. The counseling provided is also rarely informed by theory and often does not address key factors that maintain risk, like alcohol use. Web-based, brief interventions may be one approach that is well-suited to provide support alongside these programs and could help MSM participating in these programs to reduce their alcohol use and begin using HIV prevention methods that work. With previous support, we developed Game Plan, an interactive, responsive web application modeled after evidence-based brief motivational interventions. It is designed to help high-risk, heavy drinking MSM consider reducing their binge drinking and sexual risk behavior when they get tested for HIV. In a preliminary study of 40 heavy drinking, high-risk MSM, those who used Game Plan after HIV testing reported 24% fewer binge drinking days, 17% fewer alcohol problems, 50% fewer new anal sex partners, and 12% fewer high-risk condomless sex (CAS) acts compared to controls over a three-month follow-up period. The proposed study involves conducting a larger-scale study exploring Game Plan?s effects among MSM in the real-world, alongside innovative approaches for expanding HIV testing. Using a hybrid 1 effectiveness- implementation approach, we will recruit 360 high-risk, heavy drinking MSM online from several high-incidence areas in the US to participate in a program providing home-based HIV/STI self-tests in the mail at regular intervals over a year (baseline, 6 months, 12 months). Participants will be randomly assigned to receive access to either (1) a 24-hour helpline for counseling/referrals, or (2) the helpline plus Game Plan. We will test whether those who use Game Plan show lower rates of heavy drinking, any STIs, and high-risk CAS events compared to those receiving access to the helpline alone. Mixed-methods approaches will also be used with Game Plan users (N=30) and testing outreach program stakeholders (N=12) to begin understanding key implementation outcomes that can guide us in designing strategies for implementing Game Plan into HIV/STI testing programs.